Windshear is a meteorological phenomenon in which sudden inversions in the speed or direction of the wind cause local instabilities.
These highly localized and short-lasting phenomena are potentially dangerous for aircraft, in particular in phases traveling near the ground, in particular during landing or takeoff of the aircraft.
The passage of the aircraft in a windshear zone may create a sharp drop in the lift, requiring immediate actions by the crew of the aircraft to exit the zone safely.
The detection of the potential presence of shear zones in front of the aircraft and the establishment of corresponding guidance actions are therefore highly sought after to ensure flight safety.
To that end, different piloting assistance systems are known. Thus, some systems include a detection unit using a meteorological radar. The radar scans the atmosphere in front of the aircraft, for example by taking Doppler measurements, and predictively determines an alert when approaching a shear zone.
These systems generally comprise a guidance unit for the evolution of the aircraft, such that when an alert for approaching a shear zone is generated by the radar, a guidance mode of the go-around type is provided for landing and takeoff. This guidance mode is implemented by the pilot of the aircraft, by pressing a specific button.
Other detection assemblies, designated by the term “enhanced ground proximity warning system” (EGPWS), in particular use anemometric data such as the airspeed and the vertical speed to determine the presence of the aircraft in a shear zone. The detection assemblies of this type may in particular emit a reactive alert indicating the presence in a shear zone.
In that case, the unit guiding the evolution of the aircraft establishes a particular guidance mode, able to minimize the altitude loss, while maintaining an appropriate flight envelope to avoid stalling.
When these two systems are implemented together in a given aircraft, they therefore each produce specific alerts that must be addressed separately by the crew of the aircraft.
Furthermore, the procedure to be adopted is complex for the crew, when a first proximity alert created by the radar is emitted, followed by a second alert indicating presence in a shear zone, emitted by the enhanced ground proximity warning system.